The present invention relates to industrial process control or monitoring systems. More specifically, the present invention relates to wireless process field devices used in such systems.
In industrial settings, systems are used to monitor and control inventories and operation of industrial and chemical processes, and the like. Typically, the system that performs these functions uses field devices distributed at key locations in the industrial process coupled to control circuitry in the control room by a process control loop. The term “field device” refers to any device that performs a function in a distributed control or process monitoring system, including all devices used in the measurement, control and monitoring of industrial processes.
Typically, each field device also includes communication circuitry that is used for communicating with a process controller, other field devices, or other circuitry, over the process control loop. In some installations, the process control loop is also used to deliver a regulated current and/or voltage to the field device for powering the field device. The process control loop also carries data, either in an analog or digital format.
In some installations, wireless technologies have begun to be used to communicate with field devices. Wireless operation simplifies field device wiring and setup. Wireless installations are currently used in which the field device includes a local power source. However, because of power limitations, the functionality of such devices is typically limited. Further, in some instances, field devices are located at remote locations where it is difficult to visually monitor the surrounding environment. Often, a vehicle must be dispatched with service personnel in order to inspect the site. This may be many miles away and require significant travel time to visit a particularly remote location.